1. Field of the Invention
The present invention relates to a damping apparatus suitable for apparatuses--such as electron microscopes, precision optical apparatuses, measurement apparatuses, and precision balances--whose functions are adversely affected by vibrations from foundation, as well as for vibration elimination tables on which the above-described apparatuses are mounted so as to eliminate vibrations.
2. Description of the Related Art
For systems in which a vibrating body (a vibration generating section) supports a body to be vibrated (a vibration reception section), there has been developed an active control method in which a force is actively applied to the body to be vibrated, thereby preventing transmission of vibrations to the body to be vibrated.
An actuator mechanism for such active damping is disclosed in, for example, EP0701314A3.
In the actuator disclosed in EP0701314A3, a current is caused to flow through an electric conductor (drive coil) disposed within an air gap through which lines of magnetic force (magnetic field) pass, so as to generate a force to damp the vibration elimination table.
However, since the electric conductor supported within the air gap is fixed to the main body of the vibration elimination table serving as the vibration reception section, and magnetic-force-line (magnetic field) generation means having the air gap is disposed on a base serving as the vibration generation section, the magnetic-force-line (magnetic field) generation means interferes with the electric conductor if the main body of the vibration elimination table moves with respect to the base in a direction perpendicular to the direction of movement of the electric conductor, resulting in damage to the electric conductor.
The above-described problem may be overcome by widening the air gap. However, if the air gap is widened, the magnetic flux density decreases, and therefore, the efficiency of generation of a force relative to the supplied current decreases.
In addition, when the electric conductor is rigidly supported within the air gap, vibrations are transmitted from the base-side to the vibration-elimination-table side through a mechanism for supporting the electric conductor, resulting in degraded damping performance.